Stabilized scanning radar antenna



June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA Filed Aug. 9', 1950 ll Sheets-Sheet 1 m INVENTORS 40/2 5 72w 5050/ DOA/H40 BHYLE) LE /W55 C TH/ESEN (jails; ifi/HEFEE A TTOEA/EY June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA ll Sheets-Sheet 2 Filed Aug. 9, 1950 N 4 e r M NOV/E 2 mg; m mm mc T 5. 4 ED FM Z fi Mp? June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA Filed Aug. 9, 1950 ll Sheets-Sheet 3 INVENTORS Mame/7'5 TEN BOSCH DOA/H4O S. BH'YLEY 77 2/1455 C. MHTHIESEN Cn/eL F SCHHEFER H TTOEA/E Y June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA Filed Aug. 9, 1950 11 Sheets-Sheet 4 {45' I 1!! i l INVENTORS M ue/rs rE/v BOSCH DON/4L0 5. BAIYLEY JhM s C. MflTH/ESEN CHPL A" SCH/Era? June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA gave/75 m 505; NALO a r/.5

724455 C. MflTH/ESEN Caz; F 5c 4EFEE June 12, 1962 M. TEN BOSCH ETAL 3,039,095

STABILIZED SCANNING RADAR ANTENNA 11 Sheets-Sheet 6 Filed Aug. 9. 1950 June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNINGRADAR ANTENNA 11 Sheets-Sheet 7 Filed Aug. 9, 1950 5R mwwi M N E e Ew 0 V n T NBBHH 7 IN MC 4, 5 c. 5 M noww M2? June 12, 19-62 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA Filed Aug. 9, 1950 ll Sheets-Sheet 9 INVENTORS Na ve/r5 TE/V BOSCH DOA/440 .5. BflYLE) Ji/Me's C. Marv/55m CA'PL A SCHAEFEE 14 7' TOP/V5 Y June 12, 1962 M. TEN BOSCH ETAL 3,039,096

STABILIZED SCANNING RADAR ANTENNA olwuo S. BHYLE) JkMEs C. Mar/0555M June 12, 1962 M. TEN BOSCH ETAL 9 5 STABILIZED SCANNING RADAR ANTENNA ll Sheets-Sheet 11 Filed Aug. '9, 1950 Hill M 5 E P Y Y E mfg N N s 4 E P mowmfl o NB H W M 4 QMC 3,39,0% Patented June 12., 1962 IQQ STABHJIZED SCANNING RADAR ANTENNA Maurits ten Bosch, White Plains, Donald S. Bayley, Bedford Village, James C. Mathiesen, Pleasantville, and

Carl F. Schaefer, Port Washington, N.Y., assignors, by

mesne assignments, to United Aircraft Corporation,

East Hartford, Conn, a corporation of Delaware Filed Aug. 9, 1956, Ser. No. 178,458 12 Claims. (Cl. 343-761) Our invention relates to an improvement in stabilized scanning radar antennae, and more particularly to an improved stabilized scanning radar antenna for use in aircraft in which no moment is transmitted to the antenna support.

In the use of radar in aircraft for searching, bombing and the like, it is necessary to oscillate the microwave beam from side to side during the forward flight of the aircraft in order to produce a representation of the area covered upon the cathode ray tube which comprises the radar screen. The angle of oscillation may be wide in searching, as for example, 75 on each side of the center line and the speed of scanning may be such that the angle of 150 is covered every two seconds, that is, the scanning proceeds at a rate of one-half look per second. In searching it may be desirable to search a narrow area, in which case the speed of scanning can be increased to two looks per second for a search angle say of 12%. on each side of the center line. Scanning involves the changing of the direction of the beam of microwaves comprising the radar signal from side to side. This is usually accomplished by means of oscillating a reflector and the feed horn associated therewith. Since the weight of the parts is appreciable, the reaction involved in stopping the momentum of the oscillation about a vertical axis and reversing the direction of rotation must be taken up by the support. Since airplane construction is quite light, this reaction will introduce stresses into the aircraft structure and may result in vibration. Since these stresses at slow speeds of oscillation are comparatively small due to the relatively small angular momentum of the parts due to the slow speed of scanning at the rate of one-half look per second, the reaction forces are not large. Then, too, the comparatively slow speed of scanning will not set up serious vibrations. When the small angle of scan, however, is introduced and the speed of scaiming increased to two looks per second, the reaction forces due to the increased angular momentum and vibrations resulting from the increased speed of oscillation become objectionable. When a target is located and it is desired to increase the brightness of the picture on the radar screen, and when it is desired to increase the scale factor of this picture, a much more rapid scan must be introduced, say at the rate of ten looks per second. At this rate of scanning the reaction forces on the airplanes structure become seriously great and comparatively violent vibrations are introduced. Even if the airplane structure were reinforced to withstand this, the vibration has a deleterious effect on the radar parts, on the bearings and on the accuracy of the instrument.

One object of our invention is to provide a stabilized scanning radar antenna assembly which will minimize the momentstransmitted to the support of the scanning assembly.

Another object of our invention is to provide an inertia compensator which will compensate for the moments involved in stopping the direction of oscillation and ac celerating in the opposite direction in the oscillatory motion involved in the scanning so that the forces transmitted to the airplane structure supporting the scanning assembly are greatly reduced or eliminated entirely.

Another object of our invention is to provide a stabilized scanning radar antenna assembly which may oscillate for scanning at a comparatively rapid rate without introducing serious vibrations into the airplane structure.

Another object of our invention is to provide an inertia compensator for oscillatory movements accompanying the scanning motion of a radar antenna.

Other and further objects of our invention will appear from the following description.

In the accompanying drawings which form part of the instant specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIGURE 1 is a sectional view of the nose of an airplane fitted with a stabilized scanning radar antenna assembly containing one embodiment of our invention.

FIGURE 2 is a sectional view taken along the line 2-2 of FIGURE 1.

FIGURE 3 is a sectional view taken along the line 33 of FIGURE 2.

FIGURE 4 is a sectional view drawn on an enlarged scale viewed along the line 44 of FIGURE 3.

FIGURE 5 is a sectional view drawn on an enlarged scale viewed along the line 55 of FIGURE 1.

FIGURE 6 is an elevation with parts in section drawn on an enlarged scale viewed along the line 6-6 of FIG- URE 1.

FIGURE 7 is a sectional plan view viewed along the line '7-7 of FIGURE 6.

FIGURE 8 is a sectional view taken along the line 8-8 of FIGURE 7.

FIGURE 9 is a sectional view with parts broken away taken along the line 99 of FIGURE 8.

FIGURE 10 is a sectional view taken along the line Iii-10 of FIGURE 9.

FIGURE 11 is a sectional view taken along the line 11-11 of FIGURE 10.

FIGURE 12 is a sectional view drawn on an enlarged scale taken along the line 12--12 of FIGURE 11.

FIGURE 13 is a sectional View taken along the line 13I3 of FIGURE 12.

FIGURE 14 is a sectional view taken along the line 14-14 of FIGURE 13.

FIGURE 15 is a diagrammatic view showing the moments of inertia of the rotors forming part of our combination.

FIGURE 16 is a diagrammatic View showing the amplitude of scanning motion.

Referring now to FIGURE 1, the radar transmitter and receiver is housed within a casing 20 supported upon a shelf 22 in the nose of an aircraft 24 forward of the aircraft bulkhead 26. A supporting tube 28 is rotatably carried in a support 30 secured to the bulkhead 26 and is adapted to be stabilized around a fore-and-aft axis in any suitable manner which forms no part of the instant invention. The tube 28 carries a fork 34 for supporting a vertical tube or column 32 for rotation around an athwartship axis in a pair of bearings 36, as can readily be seen by reference to FIGURE 5. The tube 32 is stabilized around an athwartship axis passing through the bearings 36 in any suitable manner known to the art. A pitch motor 33, shown in FIGURE 5, carried by the support 30, drives a shaft 35 which in turn furnishes power through shaft 37 to a reversible clutch arrangement housed in housing 3? so that shaft 4 1 will rotate in one direction or the other depending on the engagement of the clutches which are controlled by a gyroscope sensitive around the pitch axis (not shown) as is well known in the art. Shaft 41 is coupled by universal joint 43 through appropriate gearing to a shaft 45 carrying a pinion 40 meshing with a gear segment '38 secured to the column 32. Rotation of the pinion 4th will thus stabilize the column 32, maintaining it in a vertical direction around the pitch axis. A pitch synchro 66 responds to this rotation and controls the clutches within housing 39 to stop the rotary motion when the correct position is reached. In a similar manner amotor 47 carried by the support casting 30 stabilizes the shaft 28 around the roll axis. The result is that the column 32 will be stabilized around both the pitch and roll axes. It will be seen that the fork is stabilized around the roll axis and the tube 32 is stabilized around the pitch axis. The tube 32 supports an inner tube 42 which is adapted to be stabilized in azimuth and with reference to which scanning movements will take place. The inner tube 42, which is stabilized around the roll axis, around the pitch axis and around the azimuth axis, furnishes a reference column or stable column with respect to which the oscillatory scanning movement is governed. The upper end of the stable column carries a stable platform 63 on which is rotatably mounted a member 65 which supports the radar feed-horn 46, the upper end of the antenna reflector 68, and a counterweight 54. The stable column supports a torque amplifier drive motor 48, a gear housing 58, and a torque amplifier 52. An azimuth synchro (not shown) controlled by a gyroscope sensitive to azimuth (not shown) controls a positioning arrangement carried by the stable platform 63, including the azimuth servo 62, causing an azimuth control member (not shown) to position the azimuth tube 42 in azimuth by means of the torque amplifier. The lower end of the reflector dish 68 is carried by a bracket 88 by means of a pin 82 which is vertically adjustable. The bracket 88 is rotatably mounted at the lower end of the vertical stable column 32. The upper portion of the reflector dish 68 is carried by a bracket 84 supported by a member 86 carried from the rotatable member 65. The orientation of the azimuth tube is transmitted to a shaft 56 controlling an azimuth expansion synchro 58 and a sweep resolver 71 which is adapted to transmit the point of orientation to the radar scope. This line of orientation is designated by the line OR shown in FIGURE 16, symmetrical to which the scanning takes place. The orientation of the azimuth tube 42 is also transmitted by a torque tube 44 to a gear 1% carried by the lower end of the stable column 32, as can best be seen by reference to FIG- URE 14. The gear 101) is mounted for rotation in bearings 182 and furnishes the means to take up the reaction of scanning which is not completely compensated for by the inertia compensators which form the principal part of this invention. The gear 108 being carried by the stable column and being constrained to follow the orientation of the azimuth tube 42 is in effect an oriented reference point with respect to which the scanning takes place. As the orientation changes, the scanning will continue with respect to the new orientation. Such changes in orientation may be relative with respect to the aircraft as is the case when the aircraft maneuvers in azimuth, that is, changes course. The orientation may be changed with respect to true north when it is desired to change the point of aim. The stable column 32 carries a lower inner sleeve or tube 104 rotatably mounted in a bearing 186, and this tube rotatably supports the bracket 80 carrying the antenna dish 68 and the inertia compensator assembly. It is this tube 104 which is driven with an oscillatory motion to accomplish the scanning on each side of the line of orientation. As the bracket 80 is moved back and forth through the angle of scanning amplitude, it carries the dish 68 with it and also the upper bracket 84, constraining the antenna horn assembly mounted on the upper rotatable member 65 to move with it. It is the inertia of all the oscillating parts which must be compensated for by our inertia compensator.

The motor 88, shown in FIGURE 4, is adapted to drive a gear 90 secured to a shaft 92 carried in the member 86. A pair of helical screw members 94 are secured to the shaft 92 and carry the bracket 84. The construction is such that rotation of the shaft 92 will move the dish 68 vertically upwardly or downwardly, depending on the direction of rotation of the shaft 92 and enabling an adjustment in a vertical direction of the antenna dish 68 to be made with respect to the end of the feed-horn 46. A fan 86 is adapted to circulate air within the nose of the plane to keep the radar housing cool. The interior of the radar housing is maintained at a predetermined pressure by means of pump 98. The microwave guide 64 from the radar is connected by a rotatable wave guide joint (not shown) to the horizontally disposed wave guide 188, shown in FIGURE 5. This communicates through a wave guide rotary joint 102 to a vertically directed wave guide 105. The wave guide 105 is connected to the feedhorn wave guide through a third wave guide rotary joint (not shown) rotatable around the azimuth axis, as is well known in the art. Power for the various prime movers is furnished through a conductor cable 183 connected to a suitable source of potential.

Referring again to FIGURE 14, a housing 188 is carried by a sleeve 114) pinned by pin 111 to the scanning sleeve 104. The sleeve also supports lower casing member 112 to which the bracket 88 is secured. The housing 188 contains a transmission gear having two gear ratios, one adapted to be used for the slow scan of two looks per second, and one adapted to be used for the rapid scan of ten looks per second. The gears are adapted to be shifted by means of solenoids, one carried in housing 187, and one carried in housing 189, shown in FIGURE 14. When both of these solenoids are energized rapid scan takes place. When only one of the solenoids is energized the gears are shifted so that a slow scan takes place. When both solenoids are deenergized the output is braked and the lower casing member becomes, in effect, fixed to the lower gear 100. The gear housing 188 supports a motor housing 114. Positioned in this housing is a motor which furnishes the power not only for the scanning, but also for the inertia compensators. The output of the transmission in the gear housing 108 drives a gear wheel 116 which carries a bevel gear 118 for rotation therewith. The gear 116 and the gear 118 are mounted for rotation about bearings 120 and 122 carried by a shaft 124.

Referring now to FIGURE 12, it will be seen that the bevel gear 118 meshes with a pair of ring gears 126 and 128 mounted respectively in bearings 130- and 132 carried by the lower casing member 112. The lower end of shaft 124 is mounted in a bearing 134 carried by the casing, and its upper end in a bearing 136. Cross-shaft 138 is formed integrally with the shaft 124, as can readily be seen by reference to FIGURE 14. The cross-shaft 138 carries an oscillatory member 140 in bearings 142 and 144. One end of the oscillatory member 140 terminates in a shaft 146 positioned in an angularly inclined, eccentrically positioned bearing 148 carried by the ring gear 128, as can readily be seen by reference to FIGURES 12 and 13. As the ring gear 128 rotates, the axis of the shaft 146 will describe a circle, thus oscillating the shaft 146 and the housing 140 of which it forms part. The housing 140, in turn, being secured to the shaft 138, will oscillate the shaft 124 of which the shaft 138 forms part. The oscillatory motion of the shaft 124 will oscillate the internally toothed gear segment 150 with a motion which is a close approximation to simple harmonic motion. The gear segment 150 meshes with the gear 152 secured to a shaft 154 mounted in bearings 156 and 158 carried by the lower casing member 112. Secured to the shaft 154 is an externally toothed gear segment 160 which meshes with the stabilized gear 100. Since the gear 100 is stationary due to the azimuth orientation heretofore described, the oscillation of the gear segment 160 will cause its shaft 154 to oscillate relative to the point of contact of the teeth of gear segment 160 with the teeth of the stable gear 100. This will cause the lower casing member 112 to oscillate, carrying with it the antenna dish 68 and the feed-horn 46 and associated parts, performing the desired scanning 5 movement which is in essence an oscillation in simple harmonic motion. The rapidity of the scanning movement is a direct function of the speed of rotation of the gear 116 which depends upon the speed of the motor in casing 114 and the gear ratio of the transmission gears in housing 108.

'It will be seen that up to this point the inertia of the moving parts is such that they have considerable momen tum. The forces involved in stopping the travel in one direction, then accelerating in the other direction, stopping, and then reversing again, will introduce serious vibrations.

The angular momentum of the system around the vertical axis in scanning is measured by the product of the angular velocity of the scanning motion and the moment of inertia of the system.

Let I equal the moment of inertia of the system around the vertical or scanning axis.

Let 9 equal the angular velocity of the scanning motion.

Let :1 equal the maximum deviation in scanning from the center line or axis of orientation.

Let on equal the instantaneous deviation from the center line of the scanning movement.

Let to equal Zn-f where f is the frequency of the scanning oscillation.

( %=wa cos wt The angular momentum of the system, therefore, can be represented as J 9 or J wa cos wt In order to compensate for the inertia as we propose, We must produce a system which will constantly produce a momentum which is equal and opposite to the momentum of the system at all instantaneous values around the vertical scanning axis.

Referring now to FIGURE 13, the gear 128 has secured thereto a cage 18%, the other side of which is rctatably supported in the lower casing member 112 in a bearing 182. The cage supports a rotor 184 secured to a shaft 186 carried by bearings 188 and 196 supported by the cage 18%. A circular fixed ring gear 192 is carried by the lower casing member 112 by means of screws 194-. A gear 196 is pinned to the shaft 186 by means of pin 1%. it will be clear that as the gear 128 rotates, the cage 18% will be carried around with it, causing the gear 196 which is in engagement with the ring gear 192 to rotate the rotor 184. It will also be observed that the rotation of the rotor 184 is a function of the rotation of the gear 128 in response to the rota-.

tion at which the oscillatory scanning movement takes place. A cage 2613 is secured to and carried by the gear 126. The other side of the cage 2% is rotatably supported by the lower casing member 112 by a bearing 202 similar to the bearing 182. The cage 211% carries a shaft 204 rotatably mounted in bearings 206 and 208. Secured to the shaft by means of pin 21% is a rotor 212 which is the same in weight and dimensions as the rotor 184. The shaft 204 carries a gear 214 pinned thereto by means of pin 216. A ring gear 218 is carried by the lower casing member 112 by means of screws 22th. As the cage 200 rotates with the ring gear 126 it will carry the gear 214 around in engagement with the fixed ring gear 218, causing the shaft 204 to rotate the rotor 212. Let us assume that the bevel gear 118 which does not appear in FIGURE 13 is rotating in a clockwise direction so that the gear 128 will be rotating in a clockwise direction as viewed from the right, and the gear 126 will be rotating in a clockwise direction as viewed from the left. This will cause the cage to carry the gear 214 away from the observer in FIG- URE 13, causing the rotor 212 to rotate in a clockwise direction as viewed from below. The gear 196 will be carried away from the observer, causing the rotor 184 to rotate in a clockwise direction as viewed from above. It will be seen that the axis of rotation of rotor 184 is rotating around a horizontal axis passing through the bearing 182 in a direction opposite from the direction of rotation of the axis of rotation of the rotor 212 around the horizontal axis passing through the bearing 2612. The rotors themselves, however, will rotate in the same direction when their spin axes are vertical and in opposite directions when their spin axes are horizontal. The moments involved in this motion are shown diagrammatically in FIGURE 15, in which the vector OA represents a clockwise direction of rotation of the lefthand rotor and the moment along the vertical axis, and the vector OA represents a clockwise direction of rotation of the right-hand rotor and the moment along the vertical axis. The axis of rotation, however, of the left-hand rotor moves in a counterclockwise direction and the axis of rotation of the right-hand rotor moves in a clockwise direction. After the driving bevel gear has moved the axis through an angle for the lefthand rotor and an equal angle for the right-hand rotor, the moment of the left-hand rotor is represented by the vector OB, and the moment of the right-hand rotor is represented by the vector O'B'. At the moments are represented by the vectors OC and OC', respectively, the direction of rotation of the rotors being clockwise in the direction of the arrows. At the moments are represented by the vectors OD and OD, respectively, and at 270 of rotation of the axes the moments are represented by the vectors OE and OE, respectively. It will be observed that the moments along the horizontal axis oppose each other, that is, the moment 0C is equal and opposite to the moment OC', and that the moment OE is equal and opposite to the moment OE, these moments acting along a horizontal axis. The moment O-A, however, and the moment O'A', as well as the moment OD and the moment O'D' which act along the vertical axis, are cumulative. For moments acting along an angle intermediate the horizontal and vertical axes, as for example, the moment OB for the left-hand rotor and the moment 0B for the righthand rotor, there will be a component OH along the horizontal axis and a component OV along the vertical axis for the left-hand rotor, and a component O'H along the horizontal axis and a component OV along the vertical axis for the right-hand rotor. The component OH will be equal and opposite to the component O'H' since the angle equals the angle in the negative direction. Similarly, the component along the vertical axis OV will be equal to the component OV along the vertical axis for the right-hand rotor, and both components will act in the same direction.

Let the moment of inertia of the left-hand rotor be I and the moment of inertia of the right-hand rotor be 1 Let the angular velocity of spin of the left-hand rotor about its axis be o and the angular velocity of spin of the right-hand rotor around its axis be ar The component OH in the horizontal plane will be represented by the expression The component in the horizontal plane of the righthand rotor will be represented by the expression Since these components are equal and opposite, their aggregate effect will be zero.

Along the vertical axis, however, the component 0V will be represented by the expression If the momentum along the vertical axis is to be compensated, the momentum of the system must be equal and opposite to the momentum around the scanning axis produced by the rotors, that is:

The angular velocities of the rotors are such that r 2 This will give a gear ratio of By use of the gear ratio derived above to spin the rotors, it will be clear that the equality necessary for balancing Will be achieved and the momentum along the vertical axis of scan will be zero, that is,

In operation the stabilizing system for the stable column 32 is actuated and the gyroscope, synchro and servomotor system of any suitable type known to the art will maintain this tube stabilized around the roll and pitch axes of the aircraft. At the same time, the azimuth gyroscope system is set into operation maintaining the azimuth control member carried by the stable column oriented in azimuth. The torque amplifier takes the movements of the azimuth control member as an input and causes the azimuth tube 42 to rotate, orienting it in azimuth. The movements of the azimuth tube are transferred by the torque tube to the azimuth gear carried by the lower end of the stable column and against which the scanning reaction for the slow or rapid 12 /2" scanning takes place, causing the rotatable lower casing member to oscillate. This oscillation is set up by energizing the motor Within the motor casing 114. Whether the slower scanning rate of two looks per second, or the rapid scan of ten looks per second, is to be effected depends on the energization of the gear shift solenoids contained in the housings 107 and NW. The movement of the lower rotatable member 112 will carry the antenna dish 68 and the feed-horn 46 around with it. The microwave beam from the feed-horn is adjusted with respect to the antenna dish by the energization of the motor 88 to rotate it in one direction or the other to raise or lower the dish with respect to the feed-horn. The radar is energized and the system will oscillate with respect to the stable column due to the drive from the motor within the casing 114 to the transmission gear box Within housing 108, the output of which drives the gear 116. This gear drives the bevel gear 118 which rotates the ring gear 128. The Z-crank arrangement, the end of which in the form of shaft 146 is positioned eccentrically of the ring gear 128, oscillates shaft 124. The oscillation of the shaft 124 rocks the internal gear segment 150, rotating the gear 152 and the shaft 154, causing the gear segment 160 to rock. Since the teeth of gear segment 160 are engaged with the stabilized gear 102' the shaft 154 will be rocked back and forth carrying with it the lower rotatable member 112 and with it the antenna dish and feed-horn in the oscillatory scanning movement. At the same time the cages 184i and 2% will be rotated causing the rotors 184 and 212 to be rotated while their axis shafts 136 and 294 are carried around by the cages. The arrangement is such that the momentum of the system in the oscillatory scanning movement will be counteracted by an equal and opposite momentum from the rotor system, as explained in detail hereinbefore. The scanning powered by the motor Within the housing 114 will always be through a fixed amplitude, say of 12 /2" on each side of an oriented center line, the orientation of which is controlled by the azimuth orientation system. The control for the azimuth synchro may be through a computer channel so that the line of orientation may be chosen and maintained depending on a large number of factors solved in a computer.

When it is desired to search through a large amplitude at a comparatively slow velocity, say through an angle of on each side of the aircraft, fore-and-aft axis at a low angular velocity of, say, one-half look per second, the comparatively small momentum will not require inertia compensation. In such case the motor within the housing 114- is braked in any position and both solenoids are deenergized locking the gear 116 and hence immobilizing the gear segment 16% in contact with the gear ltiii. The input to the torque amplifier may be shifted to another input calling for the slow search scan and constraining the azimuth tube to operate in accordance with the output of the torque amplifier. This will cause the gear 1% to oscillate, sluing the lower rotatable member 112 around with it and thus carrying the antenna and feed-horn for the search scanning movement. This portion of the assembly forms no part of the instant invention and is described in copending application of Paul H. Lang and Frederick Vicik, Serial No. 178,416 filed August 9, iG.

It will be seen that we have accomplished the objects of our invention.

We have provided a balanced oscillating system for oscillation about a predetermined axis in which the moments along said predetermined axis are balanced.

We have provided a stabilized scanning radar antenna assembly which will minimize the moments transmitted to the support of the scanning assembly.

We have provided an inertia compensator which will compensate for the moments involved in stopping the direction of oscillation and accelerating in the opposite direction in the oscillatory motion involved in the scanning so that the forces transmitted to the airplane structure supporting the scanning assembly are greatly reduced or eliminated entirely.

We have provided a stabilized scanning radar antenna assembly which may oscillate for scanning at a comparatively rapid rate Without introducing serious vibrations into the airplane structure.

We have provided an inertia compensator for oscillatory movements in general and more particularly for those accompanying the scanning motion of radar antenna.

it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. It is further obvious that various changes may be made in details within the scope of our claims Without departing from the spirit of our invention. It is therefore to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. In a balanced oscillatory system of the character described, an oscillatory member, means for mounting said member for oscillation about a predetermined axis, a prime mover, means driven by the prime mover for oscillating said member about said axis, a pair of rotors carried by said member having their respective spin axes disposed in separated planes parallel to each other and parallel to a plane passing through said predetermined axis, mounting means for each of said rotors, means for supporting respective mounting means from said member for rotation about an axis normal to said spin axis planes, means for rotating the rotors in the same direction when their spin axes extend along the direction of the predetermined axis, and means for rotating the rotor mount ing means in opposite directions, the velocity of the rotation of the rotors, the angular velocity of oscillation of the member, the velocity of rotation of said mounting means, the moment of inertia of the oscillatory member and supported parts, the moments of inertia of the rotors and the phasing of the rotary movements being such that the moments along said predetermined axis are substantially balanced.

2. A balanced oscillatory system as in claim 1, in which said means driven by the prime mover for oscillating said member comprises a gear, a shaft carried by said member parallel to said predetermined axis, a crank carried by said shaft for oscillation about an axis normal to said shaft, means for rotatably connecting said crank to said gear at a point eccentric of the axis of rotation of said gear, a gear segment driven by said shaft and carried by said oscillatory member, a reaction gear meshing with said gear segment, and means for mounting said reaction gear independent of said oscillatory system.

3. A balanced oscillatory system as in claim 1, in which said means driven by the prime mover for oscillating said member comprises a gear, a shaft carried by said member parallel to said predetermined axis, .a crank carried by said shaft for oscillation about an axis normal to said shaft, means for rotatably connecting said crank to said gear at a point eccentric of the axis of rotation of said gear, a gear segment driven by said shaft and carried by said oscillatory member, a reaction gear meshing with said gear segment, means for mounting said reaction gear independent of said oscillatory system, and means for orienting said reaction gear whereby to control the direction of the axis of the oscillatory movement of the oscillatory member.

4. In a balanced oscillatory system as in claim 1, a radar antenna, a radar feed horn, and means for supporting said radar antenna and feed born from said oscillatory member.

5. In a balanced oscillatory system as in claim 1, a radar antenna, a radar feed horn, means for supporting said radar antenna and feed horn from said oscillatory member, and means for changing the position of said feed horn With respect to said antenna along an axis parallel to said predetermined axis.

6. A balanced oscillatory system as in claim 1, in which said means for mounting said member for oscillation about a predetermined axis comprises a column, means for stabilizing said column about an axis normal to said predetermined axis, and means for stabilizing said column about an axis normal to said predetermined axis and to said second axis.

7. A balanced oscillatory system as in claim 1, in which said means for rotating the rotor mounting means comprises a pair of gears, means driven by said prime mover for rotating said gears in opposite directions, and

means for securing said gears to said mounting means, the axis of rotation of said gears being coaxial with the axis of rotation of said mounting means.

8. A balanced oscillatory system as in claim 1, in which said means for driving the rotors in the same direction when extending along the direction of the predetermined axis comprises a pair of gears, means for mounting said gears for rotation about an axis coaxial with the axis of rotation of the rotor mounting means, means for securing said gears to said rotor mounting means, means driven by said prime mover for rotating said gears in opposite directions, shafts carried by said rotor mounting means, rotors positioned upon said shafts for rotation therewith, gears carried by said shafts for rotation therewith, ring gears carried by the oscillatory member meshing with respective rotor shaft gears, said ring gears being positioned on opposite sides of respective planes in which the rotor spin axes are disposed, the construction being such that the rotation of the rotor mounting means in opposite directions will rotate the rotors in the same direction when their spin axes extend along the direction of the predetermined axis and in opposite directions when the spin axes of the rotors extend normal to the direction of the predetermined axis.

9. In a balanced oscillatory system as in claim 1, in which the moments along said predetermined axis are represented by the expression 21 .1, cos l-] woc cos M50 in which J is a moment of inertia of each of the rotors,

w, is the angular velocity of spin of each of the rotors,

5 is the angular displacement of the spin axes of the rotors with respect to said predetermined axis,

I is the moment of inertia of the oscillatory member and parts carried thereby,

to is the angular velocity of the oscillation and is equal to 2w where f is the frequency of oscillation,

a is the maximum deviation of the oscillatory movement from the axis of oscillation, and

t=time, in which the rotor mounting means are in phase to bring the spin axes of the rotors parallel to said predetermined axis and revolve at equal speeds.

10. A balanced oscillatory system as in claim 1, in which said means driven by said prime mover for oscillating said member about the predetermined axis includes a gear train having a plurality of ratios and means for shifting gear ratios whereby to oscillate said oscillatory member at a plurality of selected difierent speeds.

11. A balanced oscillatory system as in claim 1, in which said rotors are carried by said member upon opposite sides of said predetermined axis.

12. A balanced oscillatory system as in claim 1, in which said predetermined axis extends in a vertical direction and means for stabilizing said axis in said direction.

References Cited in the file of this patent UNITED STATES PATENTS 

